Hard disk drives (“HDDs”) are widely used to store digital data or electronic information for enterprise data processing systems, computer workstations, portable computing devices, digital audio players, digital video players, and the like. Generally, HDDs store data on a disk with a surface of magnetic material. A transducer head, e.g., read/write head, includes a writing component that magnetically polarizes areas of the magnetic material with one or two polarities to encode either binary zeros or ones. Thus, data is recorded as magnetically encoded areas or bits of magnetic polarity. A transducer head also includes a reading component that detects the magnetic polarity of each bit or area and generates an electrical signal that approximates the magnetic polarity. The signal is processed to recover the binary data recorded on the magnetic material.
Referring to FIG. 4, the disk 40 of conventional HDD 38 includes a substrate layer 42, a magnetic layer 44, and a protective layer 46 defining an exterior surface 48 of the disk. The transducer head 50 moves, e.g., flies, over the exterior surface 48 of the disk 40 to perform read/write operations.
Under certain conditions during operation, the transducer head 50 may contact and cause damage to the exterior surface 48. Accordingly, in an attempt to improved flyability and durability, and to reduce damage to the exterior surface 48 of the disk 40 due to contact between the transducer head 50 and the exterior surface 48 of the disk, conventional HDDs, such as HDD 38, deposit a layer of lubricant 52 on the protective layer 46 between the protective layer 46 and the transducer head 50. Generally, the lubricant layer 52 is used to reduce friction between the transducer head 50 and exterior surface 48, as well as reduce surface wear on the exterior surface 48 if and when the transducer head contacts the exterior surface.
As the transducer head 50 moves over the disk 40, the transducer head 50 desirably is spaced-apart a predetermined distance FHPA, i.e., flying height, relative to the disk 40 such that the transducer head does not regularly contact the disk 40. In the case of prior art HDD 38, the FHPA is equal to the distance between the transducer head 50 and the lubricant layer 52.
Conventionally, the lubricant of the lubricant layer 52 is a functional lubricant, such as FOMBLIN Z-DOL and Z-Tetraol. Functional lubricants include molecules with one or more functional end groups specifically designed to have a strong interaction with the disk surface, which enables each molecule to remain flat and have a good adhesion on or bond to the exterior surface 48. Further, because the functional lubricant layer 52 is used to cushion the transducer head 50 against contact with the disk 40, the lubricant must resist evaporation. Accordingly, functional lubricants typically have high molecular weight and thus low evaporation rates. For example, functional lubricants typically have molecular weights that are greater than about 2,000 g/mol and no detectable evaporation loss within about 5-10 years under normal operation temperatures, such as about 65° C.
According to some conventional manufacturing techniques, the storage disk 40 for conventional HDD 38 of FIG. 4 is made by (1) depositing a magnetic layer 44 on a substrate 42; (2) depositing a protective layer 46 on the magnetic layer 44; (3) polishing, buffing, wiping, or burnishing the protective layer; and (4) depositing a functional lubricant layer on the protective layer 52 that remains in place during operation of the HDD. In some conventional HDD manufacturing processes, the media or disk is burnished using a functional lubricant. Because functional lubricants are designed to bond with the disk, burnishing may cause damage to the disk, which can reduce the disk's resistance to corrosion.
According to another known manufacturing technique, a non-functional lubricant layer is deposited on the protective layer, and the protective layer is buffed and wiped using the non-functional lubricant. The non-functional lubricant layer is then removed from the protective layer, and a functional lubricant layer is permanently placed on the protective layer prior to operation of the conventional HDD.
Regardless of whether the first lubricant is a functional or non-functional lubricant, most conventional HDD manufacturing processes use a degreasing or cleaning procedure to remove the first lubricant used in the burnishing step. This degreasing or cleaning procedure typically requires the use of a solvent, which introduces additional tooling steps, personnel, materials, maintenance, floor area, solvent disposal problems and ultimately costs.
Although a lubricant layer between the transducer head and exterior surface of a disk may, in some instances, improve flyability and durability, and reduce friction and surface wear, the lubricant can introduce several shortcomings. For example, the efficiency and performance of HDDs are limited by the use of a lubricant layer. The distance between the transducer head and the magnetic layer is a factor in the efficiency and performance of HDDS. To increase the recording density of an HDD, the distance between the transducer head and magnetic layer must be decreased. In other words, the smaller the distance between the transducer head and the magnetic layer, the greater the ability to increase the areal or bit density of the disk, i.e., the amount of data that can be stored on the disk for a given area of the disk.
As shown in FIG. 4, the distance DPA between the transducer head 50 and the magnetic layer 44 of conventional HDD 38 is equal to the sum of the flying height FHPA, thickness of the lubricant layer 52, and thickness of the protective layer 46. Because the lubricant layer 52 has a minimum physical value equal to the molecular diameter of the lubricant, the distance DPA cannot be smaller than the sum of the flying height FHPA, thickness of the protective layer 46, and the molecular diameter of the lubricant without degrading the lubricant. Accordingly, one known shortcoming of using a functional lubricant layer on the protective layer is that the minimum distance between the transducer head and magnetic layer, and thus the recording or areal density, is physically limited by the physical properties, e.g., molecular weight or minimum thickness, of the lubricant.
Another known shortcoming of maintaining a functional lubricant layer between the exterior surface of the disk and the transducer head is lubricant build-up on the transducer head during normal operation of the HDD. For example, four conventional HDDs have been tested to determine the amount of lubricant build-up on the transducer head after normal operation. The lubricant build-up measured on the transducer heads was between 0.33 nm (3.3 Å) and 2.8 nm (28 Å). Lubricant build-up on the transducer head can damage the head, increase the head or glide noise, and increase the flying height of the transducer head. For example, according to tests, the increase in flying height was proportional to the increase in lubricant build-up on the transducer head. Ultimately, lubricant build-up can lead to poor performance, lower yield, and possibly failure of the HDD. Accordingly, to avoid lubricant build-up, many conventional HDDs have high flying heights.